1. Field of the Invention
The present invention relates to syringe cartridges used in injection devices. In particular, the present invention provides a collapsible syringe cartridge that facilitates construction of more compact injection devices and may be designed for use in injection devices generating injection forces sufficient for the delivery of viscous medicaments.
2. State of the Art
Automatic injectors (hereinafter referred to as “autoinjectors”) are well known in the medical and veterinary industries and enable the automatic injection of a desired dose of medicament to animal or human subjects. Autoinjectors are thought to exhibit several advantages relative to simple hypodermic syringes. For instance, because autoinjectors may be designed to automatically and reliably deliver a desired dose of medicament on demand, they facilitate quick, convenient, and accurate delivery of medicaments. In particular, autoinjectors are well suited for use by human subjects who must self-administer therapeutic substances.
In order to facilitate storage and delivery of medicament, autoinjectors including a needled injection mechanism generally include a syringe terminating in a needle, such as a hypodermic needle. If desired, the syringe included in an autoinjector may be provided within a syringe cartridge that is permanently or removably mounted to the autoinjector. For example, BD Pharmaceutical Systems of Franklin Lakes, N.J., manufactures the BD™ Auto-Injector, which utilizes a syringe cartridge that is removably mounted to the autoinjector and includes a pre-loaded syringe. Providing the syringe of an autoinjector within a syringe cartridge provides several potential advantages. For example, where the autoinjector is designed or manufactured as a single use device, providing the syringe within a syringe cartridge may ease manufacture of the autoinjector. In addition, where the autoinjector is designed as a multiple use device, providing the syringe of the injector within a cartridge that can be mounted and removed from the device allows a single injector body to be used to carry out multiple injections, to deliver different doses of medicament, or to deliver a range of different medicaments.
However, the syringe cartridges generally known in the art, including the cartridge used in the BD™ Auto-Injector, are not without shortcomings. For instance, state of the art syringe cartridges are typically designed for use with autoinjectors that generate injection forces ranging between about 3 lbs. to 5 lbs. Consequently, state of the art syringe cartridges are typically not suited for use with autoinjectors designed to exert injection forces of sufficient magnitude to deliver viscous medicaments, which may require injection forces exceeding 100 lbs. or more. Moreover, where state of the art syringe cartridges include a mechanism biasing the syringe in a retracted position, the syringe cartridges are typically designed such that the autoinjector must include a plunger having a length equal to or greater than the stroke of the syringe within the syringe cartridge combined with the stroke of the piston within the syringe. Such a requirement adds unnecessary length to the plunger and to the autoinjector itself. Therefore, it would be an improvement in the art to provide a syringe cartridge that is not only suitable for use with autoinjectors capable of delivering viscous medicaments, but is also designed to facilitate the fabrication of a more compact autoinjector.